.progress {
    width: 600px;
     height: 10px;
     border: 1px solid #ccc;
     border-radius: 10px;
     margin: 10px 0px;
     overflow: hidden;
 }
 /* 初始状态设置进度条宽度为0px */
 .progress > div {
     width: 0px;     
     height: 100%;
     background-color: yellowgreen;
     transition: all .3s ease;
 }